Add PaddingTest covering CSSPropertyPaddingSWTHandler

tests/org.eclipse.e4.ui.tests.css.swt/src/org/eclipse/e4/ui/tests/css/swt/PaddingTest.java

@@ -0,0 +1,159 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Lars Vogel and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Lars Vogel <Lars.Vogel@vogella.com> - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.e4.ui.tests.css.swt;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.custom.CTabFolder;
+import org.eclipse.swt.custom.CTabFolderRenderer;
+import org.eclipse.swt.graphics.Rectangle;
+import org.eclipse.swt.layout.FillLayout;
+import org.eclipse.swt.widgets.Button;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Shell;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests for {@code CSSPropertyPaddingSWTHandler}. Padding only takes effect
+ * when the target widget is a {@link CTabFolder} whose renderer exposes
+ * {@code getPadding()} returning a {@link Rectangle} and
+ * {@code setPadding(int,int,int,int)}; the handler reaches them via
+ * reflection. The default {@link CTabFolderRenderer} does not expose those
+ * methods, so the test installs a capturing subclass that does.
+ */
+public class PaddingTest extends CSSSWTTestCase {
+
+	/**
+	 * Captures arguments passed to the reflective {@code setPadding} call.
+	 * The handler invokes {@code setPadding(left, right, top, bottom)}; this
+	 * stub stores the four values in that order so the tests can assert on
+	 * them directly. Must be public so the handler's
+	 * {@code Method.invoke} from another package succeeds.
+	 */
+	public static class CapturingRenderer extends CTabFolderRenderer {
+		Rectangle padding = new Rectangle(0, 0, 0, 0);
+		int[] lastSet;
+
+		CapturingRenderer(CTabFolder folder) {
+			super(folder);
+		}
+
+		public Rectangle getPadding() {
+			return padding;
+		}
+
+		public void setPadding(int left, int right, int top, int bottom) {
+			lastSet = new int[] { left, right, top, bottom };
+			padding = new Rectangle(top, right, bottom, left);
+		}
+	}
+
+	private CapturingRenderer applyToCapturingFolder(String styleSheet) {
+		engine = createEngine(styleSheet, display);
+		Shell shell = new Shell(display, SWT.SHELL_TRIM);
+		shell.setLayout(new FillLayout());
+		CTabFolder folder = new CTabFolder(shell, SWT.NONE);
+		CapturingRenderer renderer = new CapturingRenderer(folder);
+		folder.setRenderer(renderer);
+		engine.applyStyles(shell, true);
+		return renderer;
+	}
+
+	@Test
+	void testPaddingShorthandSingleValue() {
+		CapturingRenderer renderer = applyToCapturingFolder("CTabFolder { padding: 15px }");
+		// setPadding(left, right, top, bottom)
+		assertArrayEquals(new int[] { 15, 15, 15, 15 }, renderer.lastSet);
+	}
+
+	@Test
+	void testPaddingShorthandTwoValues() {
+		CapturingRenderer renderer = applyToCapturingFolder("CTabFolder { padding: 10px 20px }");
+		// vertical 10, horizontal 20
+		assertArrayEquals(new int[] { 20, 20, 10, 10 }, renderer.lastSet);
+	}
+
+	@Test
+	void testPaddingShorthandFourValues() {
+		CapturingRenderer renderer = applyToCapturingFolder("CTabFolder { padding: 10px 15px 20px 40px }");
+		// top 10, right 15, bottom 20, left 40
+		assertArrayEquals(new int[] { 40, 15, 10, 20 }, renderer.lastSet);
+	}
+
+	@Test
+	void testPaddingTop() {
+		CapturingRenderer renderer = applyToCapturingFolder("CTabFolder { padding-top: 7px }");
+		assertEquals(7, renderer.padding.x, "top stored in Rectangle.x");
+	}
+
+	@Test
+	void testPaddingRight() {
+		CapturingRenderer renderer = applyToCapturingFolder("CTabFolder { padding-right: 8px }");
+		assertEquals(8, renderer.padding.y, "right stored in Rectangle.y");
+	}
+
+	@Test
+	void testPaddingBottom() {
+		CapturingRenderer renderer = applyToCapturingFolder("CTabFolder { padding-bottom: 9px }");
+		assertEquals(9, renderer.padding.width, "bottom stored in Rectangle.width");
+	}
+
+	@Test
+	void testPaddingLeft() {
+		CapturingRenderer renderer = applyToCapturingFolder("CTabFolder { padding-left: 11px }");
+		assertEquals(11, renderer.padding.height, "left stored in Rectangle.height");
+	}
+
+	@Test
+	void testPaddingOnNonCTabFolderIsSilentlyIgnored() {
+		// Padding on a non-CTabFolder widget must not crash. The handler's
+		// setPadding helper only acts on CTabFolder, every other widget is a
+		// no-op.
+		assertDoesNotThrow(() -> {
+			engine = createEngine("Button { padding: 10px }", display);
+			Shell shell = new Shell(display, SWT.SHELL_TRIM);
+			shell.setLayout(new FillLayout());
+			Composite panel = new Composite(shell, SWT.NONE);
+			panel.setLayout(new FillLayout());
+			new Button(panel, SWT.PUSH);
+			engine.applyStyles(shell, true);
+		});
+	}
+
+	@Test
+	void testPaddingOnDefaultRendererIsSilentlyIgnored() {
+		// CTabFolder's default renderer does not expose getPadding/setPadding,
+		// so the handler's reflective call throws NoSuchMethodException which
+		// is caught and swallowed. Locks in this behaviour: applying padding
+		// to a folder with the default renderer must not surface an error.
+		assertDoesNotThrow(() -> {
+			engine = createEngine("CTabFolder { padding: 10px 20px }", display);
+			Shell shell = new Shell(display, SWT.SHELL_TRIM);
+			shell.setLayout(new FillLayout());
+			new CTabFolder(shell, SWT.NONE);
+			engine.applyStyles(shell, true);
+		});
+	}
+
+	@Test
+	void testPaddingNonPxUnitIsIgnored() {
+		// Padding values must be in CSS_PX units; other units (em, %, etc.)
+		// fall through and the renderer keeps its previous value.
+		CapturingRenderer renderer = applyToCapturingFolder("CTabFolder { padding-top: 50% }");
+		assertEquals(0, renderer.padding.x, "non-px padding-top must be ignored");
+	}
+}